Algae are a natural and critical part of our Chesapeake and
Coastal Bays ecosystems.
Algae, like land plants, capture the suns energy and support the food web that leads
to fish and shellfish. They occur in a size range from tiny microscopic cells
floating in the water column (phytoplankton) to large mats of visible
macroalgae that grow on bottom sediments.

Algae may become harmful if they occur in an unnaturally
high abundance or if they produce a toxin. A high abundance of algae can block
sunlight to underwater bay grasses, consume oxygen in the water leading to fish kills,
produce surface scum and odors, and interfere with the feeding of shellfish and other
organisms that filter water to obtain their food. Some algal species can also
produce chemicals that are toxic to humans and aquatic life. Fortunately, of the
more than 700 species of algae in Chesapeake Bay, less than 2% of them are believed to
have the ability to produce toxic substances.

There are a number of algal species that have caused problems in Maryland
for many years and others that have only been recognized recently. For
example, there have been long standing problems with algal overabundance in
Marylandís Chesapeake and Coastal Bays, especially in
some of the tidal tributaries, due to nutrient over-enrichment and
subsequent blooms of numerous species of algae.

Economic losses from the effects of HABs may affect the commercial fishing
industry, tourism, cultural traditions, recreational and subsistence
harvests. During 1997 in Maryland across all seafood industry segments,
instead of continuing a pace of a 7.4% gain over 1996, 1997 sales for all
industry segments combined had declined by over 10% (Maryland Sea Grant).
Lost sales volume was estimated at $43 million due to Pfiesteria panic with estimated sales
without Pfiesteria panic of $253 million in the State. Additionally,
a medical team found neurological problems in persons exposed to localized
toxic outbreaks of Pfiesteria in Maryland during 1997.

Maryland has experienced severe Mahogany tides due to blooms of Prorocentrum, most notably in 2000.
The widely distributed and significant bloom levels resulted in some reduced
growth and mortality of hatchery shellfish and reduced seagrass bed
distribution within bloom regions. Indirect effects of such a bloom often
lead to low dissolved oxygen that can affect a broad array of living
resources; several fish and shellfish kills were evident in the bloom region
under such 2000 bloom conditions.

The blue-green algae Microcystis aeruginosa
also had significant blooms in the summer of 2000 in Chesapeake Bay. Algal
bloom samples tested toxic and resulted in temporary, precautionary beach
closures in the upper Bay. A bloom of
Dinophysis acuminata was detected in the Potomac River during
the winter 2001 and resulted in a temporary closure of shellfish waters. The
shellfish waters were reopened as toxin levels in oysters were found to be
below threshold levels by the U.S. Food and Drug Administration. The Coastal
Bays experienced macroalgae blooms that
concerned citizens about their effects on boating, Pfiesteria and Brown tide blooms occurred, and
potentially toxic species of Chattonella,
Fibrocapsa and Heterosigma were identified in the region for
the first time between 2000 and 2002.

Maryland DNR operates a longstanding comprehensive Chesapeake
Bay Monitoring Program that includes the regular measurement of algae. A similar
program is now being implemented for the Coastal
Bays. Both of these programs provide a safety net to insure that major
HABs are identified and appropriate actions taken which can include anything from
providing the public with general information about what is happening to following up with
public health officials to protect human health.

These programs alone are not sufficient to track all HABs or their
impacts because of the lack of monitoring stations in many areas and the
need for special techniques to identify HABs and their toxins. Localized
monitoring has been put in place in areas where potential HABs such as Chattonella, Heterosigma,
Brown Tide or Pfiesteria have been found to
reoccur during monitoring. In 2003, a shallow-water monitoring program
linked with nearshore continuous monitoring network will further enhance
our abilities to follow HABs and their effects on the Bays. Citizens have
participated in monitoring by reporting on obvious water discolorations,
odors, fish disease events and fish kills to the
Fish Health Hotline
(877) 224-7229 which prompts further
investigations into algal species present and conditions related to the
report.